VITTURI , Andrea

We exploit a model describing the breakup of weakly bound nuclei that can be used as a laboratory for testing different prescriptions that have been advanced in the literature to take into account the nearby presence of continuum states. In the model, we follow the evolution of a single-particle wave function in one dimension, initially bound...

We study the effect of the elastic transfer process on sub-barrier fusion reactions between similar nuclei. The coupling to the elastic transfer channel is described in terms of a parity dependent potential, directly obtained from the transfer form factor. Within the simple barrier penetration model, we find that this effect can account for a...

Background: The problem of the scattering of a one-neutron halo nucleus by another nucleus might involve an extremely complicated solution, particularly when breakup and rearrangement channels are to be considered. Purpose: We construct a simple model to study the evolution of a single-particle wave function during the collision of a...

A line of research has been developed to describe structure and dynamics of weakly-bound systems with one or more valence particles. To simplify the problem we are assuming particles moving in one dimension and, despite the drastic assumption, the model encompasses many characteristics observed in experiments. Within this model we can describe,...

The direct transfer of four nucleons in reactions with superfluid systems is compared with the feeding of the same final channel by a successive transfer of correlated nucleon pairs. A quantitative analysis is carried out for the reaction 120Sn+112Sn which shows the overwhelming dominance of the direct multiparticle transfer at bombarding...

It is shown that the use of a proper form factor in the study of the pygmy dipole resonance (PDR) is of paramount importance in order to determine the correct values for the relevant quantities characterizing these new modes. Form factors calculated within a microscopic model are compared with those provided by different macroscopic collective...

The program TFF calculates stripping single-particle form factors for one-neutron transfer in prior representation with appropriate perturbative treatment of recoil. Coupled equations are then integrated along a semiclassical trajectory to obtain one- and two-neutron transfer amplitudes and probabilities within first- and second-order...

We discuss the reaction mechanism associated with two-particle transfer reactions in a simple one-dimensional model. The reaction process is generated by two colliding wells and we follow in time the evolution of the two-particle wave function, initially concentrated in one of the two wells. At the end of the process one can single out the...

The phase transition in odd nuclei when the underlying even-even core nuclei experience a transition from spherical to deformed γ-unstable shapes is investigated. The odd particle is assumed to be moving in the three single-particle orbitals j=1/2,3/2, and 5/2. At the critical point in the phase transition, an analytic solution to the...

We investigate the evolution of one-particle spectroscopic intensities as a possible signature of shape phase transitions. The study describes the odd systems in terms of the interacting boson–fermion model. We consider the particular case of an odd j=3/2 particle coupled to an even-even boson core that undergoes a phase...

We investigate phase transitions in boson-fermion systems. We propose an analytically solvable model [E(5/12)] to describe odd nuclei at the critical point in the transition from the spherical to γ-unstable behavior. In the model, a boson core described within the Bohr Hamiltonian interacts with an unpaired particle assumed to be moving in the...

Pygmy dipole resonance can be populated via isoscalar probes due to the strong mixing of isoscalar and isovector components. The physical quantities are usually extracted by the use of reaction theory calculations. There, the most important ingredient is the form factor which contains all the relevant properties of the states we are dealing...

Nuclear dissociation cross sections for halo nuclei have been assumed by various authors to have a A 1/3 dependence on the target mass. These cross sections have also been considered to be a sum of the nuclear and Coulomb components. Explicit calculations of the break-up of 19C induced by various targets show that both of the above assumptions...

The exotic, neutron-rich and weakly-bound isotope 29F stands out as a waymarker on the southern shore of the island of inversion, a portion of the nuclear chart where the effects of nuclear forces lead to a reshuffling of the single particle levels and to a reorganization of the nuclear structure far from stability. This nucleus has become very...

Several aspect of shape phase transitions and critical point symmstries are reviewed inthis contribution within the frameworks of the Interacting Boson Model(IBM) and theInteracting Boson Fermion Model(IBFM) for even and odd sysstems respectively andcompared with collective geometric models. We discuss in particular the case of an...

The phase transition around the critical point in the evolution from spherical to deformed γ-unstable shapes is investigated in odd nuclei within the interacting boson fermion model. We consider the particular case of an odd j=3/2 particle coupled to an even-even boson core that undergoes a transition from spherical U(5) to γ-unstable O(6)...

The Bardeen-Cooper-Schrieffer (BCS) formalism is extended by including the single-particle continuum in order to analyse the evolution of pairing in an isotopic chain from stability up to the drip line. We propose a continuum discret ized generalized BCS based on single-particle pseudostates (PS). These PS are generated from the diagonalization...

Various aspects of shape phase transitions in even as well as odd systems are reviewed. Firstly, the case of an odd j 3/2 particle coupled to an even-even boson core that undergoes a transition from spherical limit (U(5)) to the γ-unstable limit (0(6)) is illustrated. Energy spectrum and electromagnetic transitions, in correspondence of the...

The semiclassical approach is one of the fundamental tools used to investigate and analyze heavy ion reaction processes. We show in this contribution that the evolution of the motion that emerges from the knowledge of the semiclassical amplitudes for the reaction channels as a function of time cannot be taken as a reliable representation for an...

In a recent work [arXiv:1510.03185] the use of the Transformed Harmonic Oscillator (THO) basis for the discretization of the singleparticle continuum into a Generalized Bardeen-Cooper-Schrieffer (BCS) formalism was proposed for the description of weakly bound nuclei. We make use of the flexibility of this formalism to study the evolution of the...

We investigate the phase transition in odd nuclei within the Interacting Boson Fermion Model in correspondence with the transition from spherical to stable axially deformed shape. The odd particle is assumed to be moving in the single-particle orbitals with angular momenta j=1/2,3/2,5/2 with a boson-fermion Hamiltonian that leads to the...

We investigate different aspects connected with shape phase transitions in nuclei and the possible occurrence of dynamical symmetries at the critical points. We discuss in particular the behaviour of the neighbour odd nuclei at the vicinity of the critical points in the even nuclei. We consider both the case of the transition from the...

Quadrupole moments and E2 transitions in the O(6) limit of the interacting boson model are studied within a formalism based on the intrinsic frame. We show that the values of these quantities for both ground- and β-bands can be directly obtained, to higher order in N, by suitably projecting the corresponding matrix elements associated with the...

We study heavy-ion inelastic scattering processes in neutron-rich nuclei including the full response to the different multipolarities. Among these we focus in particular on the excitation of low-lying dipole states commonly associated to the pygmy dipole resonance. The multipole response is described within the Hartree-Fock plus RPA formalism...